Jania (Corallinales, Rhodophyta) in southern Australia

Abstract

The coralline algal genus Jania Lamouroux (tribe Janieae, subfamily Corallinoideae, family Corallinaceae) contains six species on southern Australian coasts: J. micrarthrodia Lamouroux, J. pulchella (Harvey) comb. nov., J. pusilla (Sonder) Yendo, J. verrucosa Lamouroux, and two new species, J. minuta and J. parva. These species are segregated primarily on vegetative characters pertaining to fronds, intergenicula, branching, medullary organisation, and substrate preference, with reproductive features used in some cases. Four of the species are, as far as known, endemic to southern Australia: J. minuta, J. pawa, J. pulchella, and J. pusilla. Jania minuta and J. rnicrarthrodia have evolved a unique short-segmented morphology, with intergenicula containing only one or two tiers of medullary cells each. Jania micrarthrodia is a common and conspicuous epiphyte and variable in morphology depending on degree of water movement. In J. minuta, tetrasporangia are replaced by unusual sporangia, each comprised of a large two-nucleate cell, bracketed by small, uninucleate apical and basal cells. This species also forms distinctive multicellular propagules. Jania parva has delicate fronds with dichotomies that tend to diverge widely; only bisporangial and gametangial plants have been found. Jania pulchella has two types of intergenicula, 'janioid' intergenicula which in fertile plants contain conceptacles, and basal compressed and lobed 'cheilosporoid' intergenicula; it is transferred from Cheilosporum pulchellum Harvey. Jania pusilla is usually epiphytic on Cystophora spp., and has small fronds with broad intergenicula. Jania verrucosa, the most robust species, forms dense tufts on low intertidal rocks in southern Australia and in other subtropical or temperate regions.